Life Cycles: An Evolutionary Approach to the Physiology of Reproduction, Development and Ageing

ISBN-13: 9780412215209 / Angielski / Miękka / 1978 / 164 str.

P. Calow

Opis

As time progresses, biology becomes more and more fragmented and specialized and it becomes increasingly difficult to see how all the dis- parate facts fit together. It is completely proper that biologists should have sought to reduce complex biological wholes into their parts, and it is natural that studies on the products of this reduction should have diverged from more holistic studies on evolution and ecology. Yet the biological parts, what they do and how they are organized are products of an evolutionary process which fits organisms for life in particular ecological circumstances. Physiology, developmental biology, ecology and evolutionary biology must not be allowed to grow too far apart, therefore, because all these disciplines and the way their subject matters interact are crucial to understanding organisms - and it is this, it seems to me, which is the fundamental goal of the biological sciences. This book has been written in the spirit of unification and synthesis. It is, in a sense, a general biology of the organism - not, however, of organisms as static unchanging systems, but of organisms as dynamic entities which progress through a definite cycle of events from birth to maturity. The central theme, therefore, will be the life cycle, and the book is organized around the three main phases which are characteristic of all life cycles; growth (Part II), reproduction (Part III) and ageing (Part IV).

Spis treści

One Introduction.- 1 Life’s logic.- 1.1 Nature is cyclical.- 1.2 There are two ways of replicating a system.- 1.3 Evolution of a self-replicating system is more exciting.- 1.4 Life as a communication channel.- 1.5 Some simple population genetics.- 1.6 Molecular details of biological systems.- 1.7 Cellular details of biological systems.- 1.8 The organism.- 1.9 Summary.- Two Growing.- 2 life as an energy transforming system.- 2.1 Life as an open system.- 2.2 The partitioning of energy in organisms.- 2.3 Problems in trying to assess efficiency.- 2.4 Some estimates of conversion efficiency in heterotrophs.- 2.5 Photosynthetic efficiency.- 2.6 Metabolic adaptation.- 2.7 Metabolic adaptability.- 3 Life as a cellular system.- 3.1 The cell cycle and growth.- 3.2 Differentiation and growth.- 3.3 Nutrient supply and cell division.- 4 Life as a dynamic steady-state.- 4.1 Tissues in flux.- 4.2 Molecules in flux.- 4.3 Cells in flux.- 4.4 Control of cell turnover.- 5 On the adaptive significance of growing.- 5.1 There are two ways to get bigger.- 5.2 Is there any benefit in adiposity and obesity?.- Three Reproduction.- 6 How organisms reproduce.- 6.1 Mitosis and meiosis.- 6.2 Sexual dimorphism.- 6.3 Ferilization in animals.- 6.4 Events leading to fertilization in plants.- 6.5 Why sex?.- 6.6 Why two sexes?.- 6.7 Conclusions.- 7 Quantitative aspects of reproduction.- 7.1 When to reproduce and by how much?.- 7.2 Whether to reproduce all at once or repeatedly?.- 7.3 The cost of reproduction.- 7.4 Examples of reproductive strategies.- 7.5 Reproductive adaptability.- 7.6 The size and number of gametes.- Four Ageing.- 8 The ageing process.- 8.1 What happens to organisms that do not meet an unnatural death?.- 8.2 The manifestation of ageing in the individual.- 8.3 Single or multiple theories of ageing?.- 8.4 Ageing by accident or design?.- 8.5 A hypothesis based on the random, non-programmed accumulation of molecular damage.- 8.6 Conclusions.- 9 The cycle reversed.- 9.1 Degrowth in triclads.- 9.2 Physiological evidence for rejuvenation in triclads.- 9.3 Actuarial evidence for rejuvenation.- 9.4 Rejuvenation by asexual fission.- 9.5 Rejuvenation by sexual reproduction.- Five Summary and Conclusions.- References.- Index of organisms.